Re: [PATCH V2 2/2] dmaengine: tegra-adma: Add support for Tegra210 ADMA

[Jon Hunter <jonathanh@nvidia.com>]

On 06/10/15 10:32, Arnd Bergmann wrote:
> On Monday 05 October 2015 13:10:07 Jon Hunter wrote:
>> Add support for the Tegra210 Audio DMA controller that is used for
>> transferring data between system memory and the Audio sub-system.
>> The driver only supports cyclic transfers because this is being solely
>> used for audio.
>>
>> This driver is based upon the work by Dara Ramesh <dramesh@nvidia.com>.
>>
>> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> 
> This version looks much better!
> 
> Just one small comment:
> 
>> +	slave_req = dma_spec->args[0];
>> +	slave_dir = dma_spec->args[1];
>> +
>> +	if (slave_req == 0)
>> +		return NULL;
>> +
>> +	switch (slave_dir) {
>> +	case ADMA_AHUB_TO_MEM:
>> +		if (slave_req > tdma->rx_requests)
>> +			return NULL;
>> +
>> +		if (tdma->rx_requests_reserved & BIT(slave_req))
>> +			return NULL;
>> +
>> +		tdma->rx_requests_reserved |= BIT(slave_req);
>> +		break;
> 
> The rx_requests_reserved logic looks racy, if you have more than
> one concurrent request or release. Better use atomic_test_and_set()
> here and turn the variable into an atomic_t.

Ah yes, will update.

Thanks
Jon